2. History of trastuzumab resistance, defined as the development of progressive disease after trastuzumab-based therapy for metastatic breast cancer. Patient may not have received more than 2 prior trastuzumab-based regimens and one lapatinib-based regimen (either as single agent or in combination with chemotherapy)for metastatic breast cancer. Patients who develop metastatic disease during or after adjuvant or neoadjuvant trastuzumab are eligible.